FIG. 4.

DNase I susceptibility over time. Bacterial colonies (either Opa⁺ or Opa⁻) were picked from HEPES-buffered (pH 8)-agarose-based plates and were transformed with 1-μg quantities of donor DNA. Incubations were allowed to proceed for various periods of time prior to being terminated through the addition of 1 U of DNase I. The data were obtained by dividing the transformation frequency obtained following the addition of DNase I (X) by the transformation frequency obtained for a non-DNase I-treated sample (X₀). Transformation frequencies were the means of values obtained for groups of six transformed on the same day.